The general preparation of silver nanowires (10-200 aspect ratio) is known. See, for example, Angew. Chem. Int. Ed. 2009, 48, 60, Y. Xia, Y. Xiong, B. Lim, S. E. Skrabalak, which is hereby incorporated by reference in its entirety. Such preparations typically employ Fe2+ or Cu2+ ions to “catalyze” the wire formation over other morphologies. The controlled preparation of silver nanowires having desired lengths and widths, however, is not known. For example, the Fe2+ produces a wide variety of lengths or thicknesses and the Cu2+ produces wires that are too thick for many applications. Moreover, silver ions are commonly provided as silver nitrate, which can lead to nitric oxide (NO) co-production during silver nanowire preparation by this method. Because nitric oxide emissions to the air are regulated in some jurisdictions, it is desirable to develop methods that reduce its co-production.
The metal ions used to catalyze wire formation are generally primarily reported to be provided as a metal halide salt, usually as a metal chloride, for example, FeCl2 or CuCl2. See, for example, J. Jiu, K. Murai, D. Kim, K. Kim, K. Suganuma, Mat. Chem. & Phys., 2009, 114, 333, which refers to NaCl, CoCl2, CuCl2, NiCl2 and ZnCl2; Japanese patent application publication JP2009155674, which describes SnCl4; S. Nandikonda, “Microwave Assisted Synthesis of Silver Nanorods,” M.S. Thesis, Auburn University, Aug. 9, 2010, which refers to NaCl, KCl, MgCl2, CaCl2, MnCl2, CuCl2, and FeCl3; S. Nandikonda and E. W. Davis, “Effects of Salt Selection on the Rapid Synthesis of Silver Nanowires,” Abstract INOR-299, 240th ACS National Meeting, Boston, Mass., Aug. 22-27, 2010, which discloses NaCl, KCl, MgCl2, CaCl2, MnCl2, CuCl2, FeCl3, Na2S, and NaI; Chinese patent application publication CN101934377, which discloses Mn2+; Y. C. Lu, K. S. Chou, Nanotech., 2010, 21, 215707, which discloses Pd2+; and Chinese patent application publication CN102029400, which discloses NaCl, MnCl2, and Na2S.
Japanese patent publication 2008-190006 discloses co-production of nitric oxide during silver nanowire synthesis. However, the publication also discloses use of vacuum to increase the amount of nitric oxide released to the vapor phase from the reaction medium.
Q. Zhang, C. Cobley, L. Au, M. McKiernan, A. Schwartz, L.-P. Wen, J. Chen, Y. Xia, Applied Materials & Interfaces, 2009, 1, 2044, describes co-production of nitrogen dioxide (NO2) during silver nanowire synthesis.